1. Field of the Invention
The present invention relates to antennas and resonant-frequency-adjustment methods therefor, and in particular, to an antenna and a resonant-frequency-adjustment method therefor which are for use in a portable radio.
2. Description of the Related Art
Whip antennas are conventionally used for portable radio devices such as liquid-crystal televisions (90 to 800 MHz) and FM radios (75 to 90 MHz) (88 to 108 MHz in the U.S.) (hereinafter referred to generally as "portable radios"). Loop antennas are used for pagers.
A conventional whip antenna must be extended for use. In a frequency band equal to or less than 1 GHz, the length of the whip antenna needs to be 7.5 cm or longer, which makes it unstable when setting up a portable radio, and presents a problem when the radio falls.